Epoxy resin system for insitu rehabilitation of pipes

ABSTRACT

An epoxy resin/curing agent composition is provided comprising (i) at least one liquid epoxy resin, (ii) a reactive epoxy-functional diluent, (iii) a thixotroping atent, (iv) a polyamide resin, (v) a polyalkylenediamine, and (vi) 2-ethyl-4-methyl imidazole or derivaties thereof. The composition is suitable for use in insitu coating and rehabilitation processes and can withstand service at elevated temperatures.

BACKGROUND OF THE INVENTION

This invention relates to an epoxy resin composition for insiturehabilitation of pipes. In a specific aspect, the invention relates toan epoxy resin/curing agent composition suitable for use in therehabilitation of pipes which carry high-temperature fluids.

Underground fluid-transporting pipes fracture and corrode with use andage. Repair of a leaking pipe can involve time-consuming and expensiveexcavation and replacement of the damaged pipe. Excavation of a lengthof pipe is particularly difficult if the pipe is located in areas wherethe ground is frozen for long periods of time or if the pipe is locateddirectly beneath a highway or large structure. Techniques have beendeveloped for repairing underground pipe without excavation. Thesetechniques generally involve the saturation of a liner with athermosettable resin, placement of the saturated liner against the innersurface of the pipe, and cure of the resin to form a hard inner pipewithin and adhering to the original pipe.

Both polyester resins and epoxy resins have been used in such insitupipe rehabilitation processes. Epoxy resins have the advantage of beingless susceptible to shrinkage during the cure process. An epoxy resinformulation used in such a process must meet very demanding requirementsin addition to resistance to shrinkage with cure. The curing agent usedin the formulation must not be water-sensitive, as water is usuallypresent in the pipe or the exterior environment, and the system must notgenerate so much heat during the cure process as to embrittle or burnthe cured resin. Epoxy formulations containing curing agents have beendeveloped which overcome such problems inherent in insitu piperehabilitation. However, such systems are not adequate, and may degrade,for repairing pipelines which transport fluids at temperatures aboveabout 65° C., such as hot water or hot process chemicals.

It is therefore an object of the invention to provide an epoxy-basedformulation for insitu rehabilitation of pipelines in service atelevated temperatures and/or under corrosive conditions.

BRIEF SUMMARY OF THE INVENTION

According to the invention, there is provided an epoxy resin compositioncomprising (i) at least one liquid epoxy resin, (ii) a reactive diluent,(iii) a thixotroping agent, (iv) a polyamide resin, (v) apolyalkylenediamine, and (vi) 2-ethyl-4-methyl imidazole or derivativesthereof. The composition can be used in insitu coating andrehabilitation processes and can withstand service at elevatedtemperatures.

DETAILED DESCRIPTION OF THE INVENTION

It has been found that an epoxy resin system which is suitable forrehabilitating pipes for continuous service at higher temperatures, upto about 93° C., can be obtained by the use of liquid epoxy resin incombination with a curing agent comprising a polyamide resin, apolyoxyalkylenediamine, and 2-ethyl-4-methyl imidazole or derivativesthereof.

In general, polyamide resins can be any liquid polyamide resin,preferably having viscosity in the range of about 2.5 to about 4.5 poiseat 75° C. and amine equivalent weight of about 370 to about 400.Suitable polyamide resins include polyamines formed by reacting C₃₄dimerized fatty acid with a stoichiometric excess of aliphatic diprimarypolyamines such as diethylene triamine, triethylene tetramine,tetraethylene pentaamine, for example. A commercial example of asuitable polyamide resin includes EPON® Curing Agent V-40, a product ofShell Chemical Company.

Suitable polyoxyalkylenediamines generally have a polyether backbonebased either on propylene oxide or ethylene oxide or mixtures of thetwo. The preferred polyoxyalkylenediamines have the general structure:

    H.sub.2 NCH(CH.sub.3)CH.sub.2 [OCH.sub.2 CH(CH.sub.3)].sub.x NH.sub.2

wherein x is a finite number such that the number average molecularweight of the polyoxyalkylenediamine is from about 350 to about 450. Acommercial example of suitable polyoxyalkylenediamines includespolyoxypropylenediamine sold by Texaco under the trademark JEFFAMINE.

The curing agent will further contain 2-ethyl-4-methyl imidazole,derivatives of 2-ethyl-4-methyl imidazole such as cyanohydrinderivatives of 2-ethyl-4-methyl imidazole (e.g.,1-cyanoethyl-2-ethyl-4-methylimidazole), or mixtures thereof.2-Ethyl-4-methyl imidazole is preferred because of its slow reactivitywith epoxies at low temperature and suitably fast reactivity at curetemperatures.

The curing agent preferably contains from about 35 to about 55 weightpercent of 2-ethyl-4-methyl imidazole, most preferably 40 to about 50weight percent, based on the weight of the curing agent. The aminecomponent of the curing agent preferably contains from about 30 to about50 weight percent of polyoxyalkylenediamine, based on the weight ofpolyamine and polyoxyalkylenediamine. The ratio of the components mayvary so long as the resulting viscosity of the curing agent permitsconvenient handling in the intended application, preferably within therange of about 8 to about 16 poise at 25° C. For the inventioncomposition, in addition to a high heat deflection temperature, which isimportant in forming pipes for service at elevated temperatures, it isimportant that the viscosity of the resulting components are within therange so the flow of the components will be suitable for use in insituprocesses. Typically, the components of the curing agent are blendedunder a nitrogen blanket for approximately 40 minutes at about 37° toabout 44° C.

In addition to forming pipe for service at elevated temperatures, it isimportant that the viscosity of the epoxy resin/curing agent compositionbe sufficiently low to allow rapid impregnation of a liner supportmaterial and that is be slow reacting at lower temperatures of about 25°C. to about 30° C. If the flow of the resulting resin/curing agent mixis not in the proper range, the supporting fibers in the liner will notwet properly. The mix must be free flowing and wet the fibers in theshortest period of time in order to retain the maximum amount of timefor placing the liner inside the old pipe before the chemical reactionof the resin and curing agent causes the liner to become stiff. Theresulting mixture must also cure within a reasonably short time usingheat supplied by heated water. A unique feature of the invention is therelatively low curing temperature of the composition compared with itsservice temperature. The mixture can be cured at about 83° C., while thecured epoxy resin composition develops sufficient physical properties tobe placed in service at temperatures up to about 93° C. The curedcomposition has a heat deflection temperature of about 132° C. Mostepoxy resin systems must be post-cured above their heat deflectiontemperature to develop suitable properties for high-temperatureapplications.

The polyamine and polyoxyalkylenediamine components in the curing agentare also important to increase flexibility and to impart early partialcure to the resulting resin/curing agent mix. The early partial curestarts the curing reaction at a lower temperature, which results inbetter adhesion between the polymeric membrane coating on the fibers inthe liner and the cured epoxy resin matrix.

Epoxy resins suitable for the invention composition are any liquid epoxyresins, provided that they have an epoxide equivalent weight within therange of about 165 to about 195. Epoxy resins will generally havestarting viscosities within the range of about 30 to about 130 poise at25° C. Epoxy resins which have resin viscosities of less than 70 poiseare most preferred in order to impregnate fibers readily. Preferably theepoxy resin is a diglycidyl ether of a dihydric phenol. Diglycidylethers of dihydric phenols can be produced, for example, by reacting anepihalohydrin with a dihydric phenol in the presence of an alkali.Examples of suitable dihydric phenols include: 2,2-bis(4-hydroxyphenyl)propane (bisphenol-A); 2,2-bis(4-hydroxy-tert-butylphenyl) propane;1,1-bis(4-hydroxyphenyl) ethane; 1,1-bis(4-hydroxyphenyl) isobutane;2,2-bis(4-hydroxytertiarybutylphenyl) propane; bis(2-hydroxynapthyl)methane; 1,5-dihydroxynaphthalene; 1,1-bis(4-hydroxy-3-alkylphenyl)ethane and the like. The preferred dihydric phenol is bisphenol-A.Suitable dihydric phenols can also be obtained from the reaction ofphenol with aldehydes such as formaldehyde (bisphenol-F). A commercialexample of such a diglycidyl ether is EPON® Resin DPL-862, a product ofShell Chemical Company. Commercial examples of preferable epoxy resinsinclude EPON® Resin 828, EPON® Resin 826, and EPON® Resin 825, productsof Shell Chemical Company which are diglycidyl ethers of2,2-bis(4-hydroxyphenyl)propane having number average molecular weightswithin the range of about 340 to about 400. The epoxy resin can be amixture of these resins. The currently preferred epoxy resin includes amixture of diglycidyl ethers of bisphenol-A and bisphenol-F because ofthe reduced tendency of such a mixture to crystallize when stored.

The epoxy resin component preferably contains a minor amount of areactive diluent. The diluent should have more than an average of aboutone reactive group per molecule, and preferably should have a viscositywithin the range of about 0.5 to about 25 poise at 25° C. It isimportant that this diluent lower the viscosity to a useful range, butthat it not lower the heat deflection temperature of the cured resincomposition. Suitable reactive diluents include diglycidyl ether ofdiols such as the diglycidyl ethers of 1,4-butanediol and neopentylglycol; and diglycidyl ethers of carboxylic acids such as Cardura® E-10(glycidyl ester of C₉ -C₁₁ alkyl carboxylic acids sold by Shell ChemicalCompany). The diglycidyl ether of neopentyl glycol is most preferredbecause of the superior heat deflection temperature imparted to thecured resin and the desired viscosity range possible in the uncuredformulation.

A minor amount of a thixotroping agent can also be present in the epoxyresin composition. Thixotroping agents reduce the tendency of a resinmixture to flow at low shear rates. This is particularly important forholding the resin/curing agent composition in place when the system isheated to its cure temperature. Suitable thixotroping agents include anyknown silica thixotroping agent. Suitable commercial examples includeCab-O-Sil® fumed silica, a product of Cabot Corporation.

Typically the thixotroping agent is slowly blended into the epoxy resinat a temperature within the range of about 65° C. to about 72° C. in ahigh shear mixer. The reactive diluent is blended into the epoxy attemperatures within the range of about 43° C. to about 50° C. The amountof thixotroping agent and reactive diluent will vary depending on theepoxy resins, thixotroping agents or diluents used, as long as theviscosity of the resulting epoxy resin/curing agent mix is within therange of about 25 to about 65 poise at 25° C. and the amount presentdoes not substantially lower the heat deflection temperature of thecured resin. Weight per epoxide of the epoxy resin component, includingthe epoxy resin, reactive diluent, is preferably within the range ofabout 160 to about 195. Preferably the thixotroping agent is presentwithin the range of about 0.5 to about 5 weight percent based on theepoxy resin component. Preferably the reactive diluent is present withinthe range of about 0.1 to about 15 weight percent based on the epoxyresin component.

For the epoxy resin formulation to be useful for the insitu repair ofpipes, the formulation should (1) be low enough in viscosity to wet theliner used in the repair in the shortest time possible, preferably fromabout 25 to about 65 poise, (2) have the correct thixotropic propertiesto prevent resin run down on heating during the cure cycle, (3) be slowreacting at low temperature to prevent premature gelation, (4) be ableto cure below about 83° C. (temperature of heated water), preferably atabout 70° C. to about 83° C., and (5) develop suitable physicalproperties in a few hours. The invention liquid epoxy resin formulationsfulfill the above requirements, when thoroughly mixed at about 100 partsof the resin component to about 6 to about 12 parts, preferably about 8to about 11 parts, of the curing agent. The term "liquid" means normallyliquid at ambient temperature and pressure.

The epoxy resin component and the curing agent should be brought to atemperature of about 24° C. to about 27° C. prior to mixing. Mixing timewill typically be about 10 to about 20 minutes depending on theefficiency of the mixer. If the mix is low in temperature, it will bethick and will not wet out a liner efficiently.

Methods for lining a pipe or a passageway with a hard liner are taught,for example, in U.S. Pat. Nos. 4,009,063; 4,064,211; 4,135,958 and4,758,454, the disclosure of which are herein incorporated by reference.The liners are generally a laminate of nonwoven felt coated with aplastic sheet material as a membrane. The felt fibers are impregnatedwith an uncured resin/curing agent mix. The felt acts as a carrier forthe resin mix and keeps the resin in a convenient form until it iscured. The impregnated liner is turned inside out along the passagewayinside a pipe using fluid pressure. When the resin is cured, the fibrouslayer impregnated with resin forms a rigid shell inside the pipeline orpassageway, defining a smooth inner surface to the lining.

Suitable felt fibers to act as a support for the epoxy resin systems,for example, can be composed of polyester or glass fibers. The felt istypically coated on one side with a thin layer of a thermoplasticcoating (membrane). The membrane holds the resin/curing agentcomposition inside the impregnated felt and prevents water fromcontacting the resin mixture during a hot water cure. The membranetypically is a single layer such as polyurethane, for example, but canbe composed of several layers. The first layer can be a bonding layerbetween the fibers and the second layer, which optionally can be abarrier film such as ethylene vinyl alcohol. The bonding layer, forexample, can be an ionomer such as Surlyn polymer (a polyethylenecopolymer that is lightly crosslinked via interchain ionic bonds withmetallic acrylates). An outer film can be a PVC (polyvinyl chloride)film, a urethane film such as polyurethane or Surlyn polymer. Surlyn ispreferred because of the lower water permeability. Optionally, themembrane can be removed once the epoxy resin system is cured.

The felt is impregnated with the epoxy resin/curing agent miximmediately prior to use. Working life of the liner can be extended tomore than 2 days if packed in ice. For a 9 mm thick liner, the epoxyresin mix of the invention is typically cured in a cure cycle of aboutone hour at about 50° C., about one hour at about 70° C., and about fourto five hours at about 83° C., to produce a crosslinked resin matrixwith a heat deflection temperature of about 132° C., which correspondsto service temperature of up to about 93° C. Depending on the heatapplied, the resin matrix may not be completely cured until the pipe isplaced in service at elevated temperature, which will further cure theresin matrix. Heat can be supplied by any method that enablescirculation of heat through a pipe, such as hot water, steam or hot air.Hot water is preferred because of ease of controlling the temperature ofthe system. The cured composite liner should be cooled slowly at a rateof about 5° C. per hour or less in order to relieve residual stresses.The cured composite from the invention epoxy resin formulation retainsgood physical properties at temperatures up to about 93° C.

EXAMPLE 1

This example demonstrates preparation of an epoxy resin compositionaccording to the invention. Table 1 below describes the epoxy resincomponent of the compositions.

The epoxy resin composition of run 1 was prepared as follows: 800 gramsof the diglycidyl ether of 2-2-bis(4-hydroxyphenyl)propane (liquid epoxyresin) having a weight per epoxy in the range of about 175 to about 185and viscosity of about 60 to about 70 poise were placed in a metal quartcontainer and heated to 71° C. 8 grams of Cab-O-Sil M-5 (available fromCabot Corp.) were slowly added to the liquid epoxy resin while mixing ata high shear rate. After the mixture was cooled to about 45° C., 40grams of neopentyl glycol glycidyl ether were blended in with a stirrerattached to an air motor using a lower rate of shear. The resultingresin blend was then poured into a glass quart jar and left to cool toroom temperature and to allow entrained air bubbles to escape.

The epoxy resin composition of run 2 was prepared as follows: 500 gramsof the diglycidyl ether of 2,2-bis(4-hydroxyphenyl)propane (liquid epoxyresin) having a weight per epoxy in the range of about 175 to about 185and viscosity of about 60 to about 70 poise at 25° C. were placed in ametal quart container and heated to 71° C. 5 grams of Cab-O-Sil M-5(available from Cabot Corp.) were slowly added to the liquid epoxy resinwhile mixing at a high shear rate. After the mixture was cooled to about45° C., 25 grams of Epoxide 8 (C₁₂ -C₁₄ alkyl glycidyl ether availablefrom Shell Chemical Co.) were blended in with a stirrer attached to anair motor using a lower rate of shear. The resulting resin blend wasthen poured into a glass quart jar and left to cool to room temperatureand to allow entrained air bubbles to escape.

Run 3 was prepared in a similar manner to run 2, except 500 grams of thediglycidyl ether of 2,2-bis(4-hydroxyphenyl)propane having a weight perepoxy in the range of about 180 to about 195 and viscosity of about 110to about 150 poise at 25° C., 40 grams of Epoxide 8 and 8 grams ofCab-O-Sil M-5 were used.

Run 5 was prepared in a similar manner to run 1, except 500 grams of thediglycidyl ether of 2,2-bis(4-hydroxyphenyl)propane having a weight perepoxy in the range of about 172 to about 178 and viscosity of about 40to about 60 poise at 25° C., 25 grams of neopentyl glycol glycidyl etherand 7.5 grams of Cab-O-Sil were used.

Run 6 was prepared in a similar manner to run 1, except 500 grams of thediglycidyl ether of 2,2-bis(4-hydroxyphenyl)propane having a weight perepoxy in the range of about 180 to about 195 and viscosity of about 100to about 150 poise at 25° C., 25 grams of neopentyl glycol glycidylether and 5 grams of Cab-O-Sil were used.

Properties of these epoxy resin components are shown in Table 1 below.

                                      TABLE 1                                     __________________________________________________________________________    Resin Composition, % Weight                                                                  1  2  3   4   5   6                                            __________________________________________________________________________    Liquid Epoxy Resin*                                                                          94.3                                                                             94.3                                                                             .sup. 91.0.sup.1                                                                  100.0                                                                             .sup. 93.9.sup.2                                                                  .sup. 94.3.sup.1                             Diglycidyl Ether NPG                                                                          4.7                                                                             -- --  --   4.7                                                                               4.7                                         Epoxide 8      --  4.7                                                                              8.0                                                                              --  --  --                                           Cab-O-Sil       1.0                                                                              1.0                                                                              1.0                                                                              --   1.4                                                                               1.0                                         Properties                                                                    Epoxy Equivalent Weight                                                                        178                                                                              187                                                                              195                                                                               178                                                                               178                                                                               189                                        Viscosity, cp @ 25° C.                                                                3,950                                                                            3,870                                                                            4,500                                                                             7,150                                                                             7,600                                                                             7,650                                        __________________________________________________________________________     *diglycidyl ether of 2,2bis(4-hydroxyphenyl)propane having a weight per       epoxy in the range of about 175 to about 185.                                 .sup.1 weight per epoxy in the range of about 180 to about 195.               .sup.2 weight per epoxy in the range of about 172 to about 178.          

Compositions from run 1 and 5 have suitable mix viscosities andexcellent heat deflection temperature as indicated in run A and run D inExample 4 (see Table 4). Run 4, without the diluent, is too viscous andresults in very viscous mix as indicated in run E, which did not wet theliner properly. The comparative example, run 2 has suitable viscosity,but the Epoxide 8 diluent lowers the heat deflection temperature of theresulting laminates as shown in Example 4 run B.

EXAMPLE 2

This example demonstrates preparation of an epoxy resin compositionaccording to the invention containing Cardura® E10 as the reactivediluent in place of neopentyl glycol glycidyl ether. Table 2 belowdescribes the compositions of epoxy resin components. Properties of thecompositions are listed in Table 2.

The epoxy resin composition of run 1 was prepared as described inExample 1 run 2.

The epoxy resin composition of run 2 was prepared as follows: 500 gramsof the diglycidyl ether of 2-2-bis(4-hydroxyphenyl)propane (liquid epoxyresin) having a weight per epoxy in the range of about 175 to about 185and viscosity of about 60 to about 70 poise were placed in a metal quartcontainer and heated to 71° C. 5 grams of Cab-O-Sil M-5 (available fromCabot Corp.) were slowly added to the liquid epoxy resin while mixing ata high shear rate. After the mixture was cooled to about 45° C., 25grams of Cardura® E10 (glycidyl ether of C₉ -C₁₁ alkyl carboxylic acidsavailable from Shell Chemical Company) were blended in with a stirrerattached to an air motor using a lower rate of shear. The resultingresin blend was then poured into a glass quart jar and left to cool toroom temperature and to allow the air bubbles to escape.

The epoxy resin composition of run 3 was prepared in a similar manner torun 2, except 15 grams of Cardura® E10 was blended into the mixture.

The epoxy resin composition of run 4 was prepared in a similar manner torun 3, except a liquid epoxy resin (diglycidyl ether of2-2-bis(4-hydroxyphenyl)propane) having a weight per epoxy in the rangeof 172 to about 178 and viscosity of about 40 to about 60 poise at 25°C. was used.

Properties of these epoxy resin components are shown in Table 2 below.

                  TABLE 2                                                         ______________________________________                                        Resin Composition, % Weight                                                                     1      2       3    4                                       ______________________________________                                        Liquid Epoxy Resin*                                                                             94.3   94.3    96.0 .sup. 96.0.sup.1                        Epoxide 8          4.7   --      --   --                                      Cardura ® E-10                                                                              --      4.7    3    3                                       Cab-O-Sil          1.0    1.0     1.0  1.0                                    Properties                                                                    Epoxy Equivalent Weight                                                                           187    186     184                                                                                182                                   Viscosity, cp @ 25° C.                                                                   3,870  5,010   5,900                                                                              3,660                                   ______________________________________                                         *diglycidyl ether of 2,2bis(4-hydroxyphenyl)propane having a weight per       epoxy in the range of about 175 to about 185.                                 .sup.1 weight per epoxy in the range of about 172 to about 178.          

The viscosity of the resulting epoxy resin mix is too high in Table 2run 3 as indicated by the high mix viscosity in Example 4 run K (Table4). A mix viscosity at 8,920 cps is too viscous to wet a felt linerproperly. Run 4, containing a lower viscosity liquid epoxy resin andCardura® E-10 diluent provides for a suitable mix with proper viscosityand a good heat deflection temperature as shown in Example 4 run L.

EXAMPLE 3

Table 3 below describes the composition of the curing agent component.The curing agent composition of run 1 was prepared as follows: 60 gramsof polyamine resin composed primarily from polyamine resin with 5 toabout 10% ethylene amines formed by reacting C₃₄ dimerized fatty acidwith a stoichiometric excess of ethylene amines includingtriethylenentetraamine and 40 grams of polyoxypropylenediamine having anaverage molecular weight of approximately 400 and 80 grams of2-ethyl-4-methyl imidazole were placed into a 8 ounce glass jar andmixed with a spatula. The jar was then sealed and placed on a sampleroller for approximately 2 hours.

Run 2 was prepared in a similar manner to run 1, except without theimidazole. 120 grams of polyamine resin and 80 grams ofpolyoxypropylenediamine were used.

Run 4 was prepared in a similar manner to run 1, except 80 grams of2-propyl imidazole were used instead of 2-ethyl 4-methyl imidazole.

                  TABLE 3                                                         ______________________________________                                        Curative Composition,                                                         % Weight        1        2      3       4                                     ______________________________________                                        2-ethyl 4-methyl                                                                              44.5     --     100.0   --                                    imidazole                                                                     2-propyl imidazole                                                                            --       --     --      44.5                                  Jeffamine D-400*                                                                              22.2     40.0   --      22.2                                  EPON Curing Agent V-40**                                                                      33.3     60.0   --      33.3                                  Properties                                                                    Viscosity, cp @ 25° C.                                                                 1,200    800    13,800  700                                   Amine number, % 10.5     8.0     12.0   9.5                                   ______________________________________                                         *Polyoxyalkyleneamine available from Texaco                                   **Polyamide curing agent available from Shell Chemical Company           

As can be seen from Table 3, 2-ethyl-4-methyl imidazole alone is tooviscous at 13,800 cp. The polyamine and polyoxyalkylenediamine lower theviscosity to the proper range at 1,200 cp, indicated by run 1. They alsoimpart flexibility to the cured system and early partial cure. Thecurative of run 3 by itself is slower to react and requires extendedheating at about 83° C. to cure whereas the invention curing agent, run1, achieves partial cure at about 60° C. within a reasonable time,preferably less than about eight hours. In run 1, partial cure wasachieved in about four to five hours at about 60° C. This results inearly partial cure and provides improved adhesion of the coatingmembrane to the resin matrix. The 2-propyl-imidazole curing agent of run4 does not give the desired heat deflection temperature as shown inExample 4 run F.

EXAMPLE 4

This example demonstrates preparation of a curable epoxy resincomposition according to the invention. Table 4 describes thecomposition containing epoxy resin components from Examples 1 and 2, andcuring agent from Example 3.

The following composites plaques were prepared to measure the physicalproperties. Plaque A was prepared by mixing 400 grams of resin from Run1, Example 1 with 36 grams of curing agent from run 1, Example 3. Apiece of polyester felt was then saturated with the resin curing agentmixture. This felt was then placed in a Teflon® coated mold and placedin a press set at 10 psi. The plaque was cured for 1 hour at 49° C., 1hour at 71° C. and 4.5 hours at 83° C. The plaque was then cut andtested for tensile strength according to ASTM method D-638 and flexuralstrength according to ASTM method D-790 at 25° C. The results are shownbelow.

    ______________________________________                                        Physical Properties of Laminate                                               ______________________________________                                        Temperature  23° C.                                                                         49° C.                                                                           71° C.                                                                       93° C.                            Strength Retention                                                            Tensile, N/mm.sup.2                                                                        39.0    37.0      34.1  26.3                                     Flexural, N/mm.sup.2                                                                       61.4    59.5      55.8  49.6                                     Modulus Retention                                                             Tensile, N/mm.sup.2                                                                        3385    2999      2613  2068                                     Flexural, N/mm.sup.2                                                                       3723    2799      2854  2208                                     ______________________________________                                    

The viscosities were measured immediately after mixing the resin andcuring agent. The heat deflection temperatures were determined accordingto ASTM method D 648-72 using the same cure schedule as that used toprepare the composite plaque.

Runs B-E and I-L were prepared using 200 grams of epoxy resincompositions listed in Table 4 and 18 grams of corresponding curingagents listed in Table 4 in a similar manner to run 1. The propertiesare shown in Table 4. Runs F and G were prepared in a similar manner,except they were cured for 1 hour at 49° C. and 3 hours at 71° C.

Run H was prepared using 100 grams of the epoxy resin component and 50grams of the curative listed in Table 4. The test bar was cured for 3hours at 71° C.

The viscosities and the heat deflection temperature of these samples areshown in Table 4.

                                      TABLE 4                                     __________________________________________________________________________    Composition,                                                                  % Weight A  B  C  D  E  F  G  H  I  J  K  L                                   __________________________________________________________________________    Resin Component                                                               Example 1-1                                                                            91.7                                                                             -- -- -- -- 91.7                                                                             -- -- --                                           Example 1-2                                                                            -- 91.7                                                                             -- -- -- -- -- -- --                                           Example 1-3                                                                            -- -- 91.7  -- -- 91.7                                                                             66.7                                                                             --                                           Example 1-4                                                                            -- -- -- -- 91.7                                                                             -- -- -- --                                           Example 1-5                                                                            -- -- -- 91.7                                                                             -- -- -- -- --                                           Example 1-6                                                                            -- -- -- -- -- -- -- -- 91.7                                         Example 2-2                         91.7                                                                             -- --                                  Example 2-3                         -- 91.7                                                                             --                                  Example 2-4                         -- -- 91.7                                Curing Agent                                                                  Example 3-1                                                                             8.3                                                                              8.3                                                                              8.3                                                                             8.3                                                                              -- -- -- --  8.3                                                                              8.3                                                                              8.3                                                                              8.3                                Example 3-2                                                                            -- -- -- -- -- -- -- 33.3                                                                             --                                           Example 3-3                                                                            -- -- -- --  8.3                                                                             -- -- -- --                                           Example 3-4                                                                            -- -- -- -- --  8.3                                                                              8.3                                                                             -- --                                           Example 3-5                                                                            -- -- -- -- -- -- -- -- --                                           Properties                                                                    Mix Viscosity,                                                                         4,500                                                                            5,120                                                                            6,200                                                                            5,400                                                                            8,500                                                                            5,580                                                                            7,500                                                                            3,500                                                                            5,800                                                                            7,760                                                                            8,920                                                                            5,680                               cps @ 25° C.                                                           Heat Deflection,                                                                         132                                                                              124                                                                              105                                                                              134                                                                              142                                                                              106                                                                              93                                                                               52                                                                               129                                                                              120                                                                              119                                                                              125                               deg. C.                                                                       __________________________________________________________________________

The samples for room temperature and heated oil soaks were prepared bysaturating 6 mm, 6 denier uncoated polyester felt with the resin/curingagent mix of run 1. The samples for high temperature water soak weremade using 3 mm, 6 denier polyester felt coated with polyurethane orSurlyn-nylon films. The samples were prepared in a heated pneumaticpress with pressure applied to produce laminates with a resin content of78 to 82 percent by weight. The samples were cured for one hour at 50°C., one hour at 70° C. and 4.5 hours at 83° C.

After immersing the samples in water or oil they were removed, wipedclean, rinsed with water, air dried for one and one-half hours andweighed. The flexural strength and modulus were determined using ASTMmethod D-790 at 25° C. on 2×5 inch coupons cut from the compositeplaques. The results are shown below.

    ______________________________________                                                       WEEKS                                                                         2   4        8      14                                                        PERCENT WEIGHT                                                                GAIN IN WATER                                                  ______________________________________                                        Coated with Polyurethane                                                      @ 66° C.  1.5   1.9      2.5  2.7                                      @ 93° C.  2.2   3.1       4.5*                                                                               6.3*                                    Coated with Surlyn                                                            @ 66° C.  1.5   2.4      2.4  2.7                                      @ 93° C.  2.5   3.0      3.1  3.3                                      ______________________________________                                                 WEEKS                                                                         4   8       12    22       30   52                                            PERCENT WEIGHT GAIN                                                  ______________________________________                                        Kerosene @ 25 C.                                                                         1.1   1.4     1.0                                                  No. 6 Oil @ 25 C.                                                                        0.7   1.1     1.1                                                  @ 66 C.    1.3   2.1     1.2                                                  @ 93 C.    1.6   1.5     1.4 0.48     0.25 0.41                               @ 110 to 116 C.                                                                          1.6   7.8     7.0 Dark and                                                                      Warped                                           ______________________________________                                                         Flexural     Flexural                                                         Strength, N/mm.sup.2                                                                       Modulus, N/mm.sup.2                             ______________________________________                                        Control Sample   51.72        3199                                            Samples Immersed                                                              12 Weeks in:                                                                  Kerosene @ 25 C. 49.64        3275                                            No. 6 Oil @ 25 C.                                                                              49.64        3275                                            @ 66 C.          44.13        2820                                            @ 93 C.          46.20        2930                                            @ 110 to 116 C.  28.27        2117                                            ______________________________________                                         *Weight gain due to the polyurethane film degradation                    

As can be seen from Table 4, the compositions A, D, I and L areparticularly suitable for use in pipe rehabilitation in which the pipesmust carry liquids and gasses at elevated temperatures. They have highheat deflection temperature compared to compositions such as H and alsohave appropriate mix viscosities.

The laminate of run 1 retained nearly 60% of room temperature physicalproperties at temperatures of up to 93° C. and withstood heated oil forprolonged periods at this temperature. No significant change in colorwas observed when the coated laminates were soaked in hot water, andonly gained about 3 weight percent at 93° C.

Chemical Resistance of Laminate

The samples for testing chemical resistance were prepared by saturating6 mm, 6 denier uncoated polyester felt with the resin/curing agent mixof run A from Example 4. The samples were prepared in a heated pneumaticpress with pressure applied to produce laminates with a resin content of78 to 82 percent by weight. The samples were cured for one hour at 50°C., one hour at 70° C. and 4.5 hours at 82° C. 2×5 inch coupons were cutfrom the composite plaque. After soaking for one year at roomtemperature, (Sample H was soaked for 12 weeks) the samples were removedfrom the chemical environment, wiped clean, rinsed with water, air driedfor one and one-half hours and weighed. Percent weight change wasmeasured. The results of the tests are shown in Table 5.

                  TABLE 5                                                         ______________________________________                                                 PERCENT WEIGHT CHANGE                                                         AFTER ONE YEAR SOAK                                                           Sample A  Sample G  Sample H*                                        ______________________________________                                        Acetone    2.2         5.5       20.8                                         20% Acetic acid                                                                          2.0         2.4       32.4                                         Toluene    0.5         0.9       24.7                                         20% Sulfuric                                                                             2.4         1.3       4.1                                          Water      2.0         1.5       1.5                                          Clorox     1.9         0.6       1.2                                          20% NaOH   1.9         0.2       nil                                          ______________________________________                                         *After 12 weeks.                                                         

As can be seen from Table 5, sample A had much better overall chemicalresistance compared to sample H. For some chemicals, such as acetone,sample A had superior resistance compared to both samples G and H.

We claim:
 1. A liquid epoxy resin composition comprising:(a) at leastone liquid epoxy resin having an epoxide equivalent weight within therange of about 165 to about 195; (b) a minor amount, relative to theliquid epoxy resin, of an epoxide functional reactive diluent; (c) aminor amount, relative to the liquid epoxy resin, of a thixotropingagent; (d) an effective amount of a liquid curing agent comprising(i) apolyamide resin; (ii) a polyoxyalkylenediamine; and (iii) from about 35to about 55 weight percent, based on the weight of component (d), of2-ethyl-4-methyl imidazole or a derivative thereof.
 2. The compositionof claim 1 wherein the relative diluent comprises a diglycidyl ether ofneopentyl glycol.
 3. The composition of claim 1 wherein the reactivediluent comprises a glycidyl ester of a C₉ -C₁₂ tertiary carboxylicacid.
 4. The composition of claim 2 wherein the polyoxyalkylenediamineis a polyoxypropylenediamine having a number average molecular weightwithin the range of about 350 to about
 450. 5. The composition of claim1 wherein the viscosity of the epoxy resin composition is within therange of about 25 to about 65 poise at 25° C.
 6. The composition ofclaim 1 in which the polyoxyalkylenediamine is present in an amount offrom about 30 to about 50 percent by weight based on (d)(i) and (d)(ii).7. The composition of claim 1 in which (d)(iii) is 2-methyl-4-ethylimidazole.
 8. The composition of claim 1 wherein the diluent is adiglycidyl ether of neopentyl glycol and the thixotroping agent is fumedsilica.
 9. The composition of claim 1 wherein (d)(i) is a polyamideresin having an amine equivalent weight of about 370 to about 400;(d)(ii) is polyoxypropylenediamine having a number average molecularweight within the range of about 350 to about 450; and (d)(iii) is2-ethyl-4-methyl imidazole.
 10. The composition of claim 9 wherein thereactive diluent is a diglycidyl ether of neopentyl glycol and thethixotroping agent is fumed silica.
 11. The composition of claim 1wherein the liquid epoxy resin is a mixture of the diglycidyl ethers of2,2-bis(4-hydroxyphenyl)propane and bis(4-hydroxyphenyl)methane.